Z axis motors consistently becoming faulty

Warm regards everyone,

I assembled a prusa i3 using reprap for info and Amazon for parts.

The first problem I encountered was the z axis motors failed to move in one direction (upwards). I replaced them with non standard 10 kg-cm motors thinking that maybe more torque will make them fail proof. But less than 1 month after the replacement, these new and bigger motors started having the same problem. Does anyone know why this is happening?

I regularly oil all 3 axes and the motion of up direction is not too tight, that I've checked.

One issue that I've always had is the earthing. One can get a small shock by touching the vertical frame or the aluminum bed, but not the motors. Could this be, in any way, the root cause of my motors going bad?

My guess is that you have both Z motors connected to the output of a single driver. If you have connected them in parallel (which is how RAMPS and many other 8-bit controller boards connect 2 Z motor connectors), then the driver needs to supply double the current. So if the driver is not getting hot and neither are the motors, turn up the current. If the Z driver is already getting hot, then you may get better results with the motors connected in series. Post the specifications of your Z motors here for more detailed advice.

Edited 1 time(s). Last edit at 06/03/2018 06:09PM by dc42.

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Large delta printer [miscsolutions.wordpress.com], E3D tool changer, Robotdigg SCARA printer, Crane Quad and Ormerod

Disclosure: I design Duet electronics and work on RepRapFirmware, [duet3d.com].

This picture that I very attached shows exactly how I have connected z axis motors.

Quote
Vatsal J Tanna
This picture that I very attached shows exactly how I have connected z axis motors.

You connected them in parallel.

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Large delta printer [miscsolutions.wordpress.com], E3D tool changer, Robotdigg SCARA printer, Crane Quad and Ormerod

Disclosure: I design Duet electronics and work on RepRapFirmware, [duet3d.com].

Yes. Now tell me how do I increase the current of the driver. Remember, I am a mechanical engineer with little background in electronics, so it would be nice if you could explain it like you are explain it to a small kid.

"Yes. Now tell me how do I increase the current of the driver"
Now read this

Increased the current. Only the motor driver (A4988) became hot. No other changes seen.